The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Vehicles employ propulsion systems including multi-mode powertrain systems that generate and transfer tractive power to a driveline in response to an operator request, including tractive power for accelerating and braking. A propulsion system can experience an operator-discernible noise or clunk during a transition between a driven state and a non-driven state. This transition is known to occur when the operator request includes either an accelerator pedal tip-in or an accelerator pedal tip-out. A driven state occurs when the propulsion system generates positive torque to spin the driveline to propel the vehicle. A non-driven state occurs when the propulsion system is not generating positive torque, e.g., is reacting driveline torque and the vehicle momentum through the vehicle wheels is driving the propulsion system through the driveline. A transition from a driven state to a non-driven state can happen when the operator removes their foot from the accelerator pedal (tips out). A transition from a non-driven state to a driven state can happen when the operator applies their foot to the accelerator pedal (tips in). A lash zone exists in a gap between meshed gears in the transmission gearbox and driveline. When the propulsion system is in the driven state, the meshed gears are in contact and transfer torque on one gear face. When positive torque associated with the driven state is removed and the wheels start to drive the propulsion system, there is a point where the meshed gears transition across the lash zone to transfer torque on the other gear face. During the gear transition across the lash zone, the driveline can accelerate and impact the other gear face, generating the clunk.